The use of Nasal Continuous Positive Airway Pressure (nasal CPAP) to treat Sleep Disordered Breathing (SDB) was pioneered by Sullivan, e.g., see U.S. Pat. No. 4,944,310. Apparatus for providing nasal CPAP typically comprises a source of air at positive pressure (for example provided by a blower or flow generator), some form of patient interface or respiratory mask system (for example a nasal or full-face mask system), and an air delivery tube.
Respiratory mask systems typically include some form of cushioning element (a “cushion”), a sealing element and some form of stabilizing element (for example, a frame and headgear). The cushioning and sealing elements may be formed in one piece, or more than one piece, or may be separate structures. Cushioning and sealing elements may be formed from different portions of a single structure. Headgear may consist of an assembly of soft, flexible, elastic straps. They may be constructed from a composite material such as foam and fabric.
The frame may be a rigid or semi-rigid structure that allows for the connection of the undercushion, headgear and air delivery tube. The frame can be made of polycarbonate, silicone or various other materials.
Much mask design effort is directed towards improving the comfort of masks. A range of commercial mask systems are known including the MIRAGE mask, manufactured by ResMed Limited.